(1) Field of the Invention
The present invention relates generally to connecting hydrophone elements in linear arrays, and more particularly to a means for connecting elements to pass a sensing material, such as optical fiber, from one hydrophone element to another without adversely affecting the sensing material or measurement sensitivity.
(2) Description of the Prior Art
Hydrophone is a generic term describing a transducer that detects or monitors underwater sound. Hydrophones are typically pressure-actuated sensors and form the basis of sonar systems. Fiber-optic hydrophones employ fiber-optic cabling to sense pressure generated by acoustic wavefronts. Acoustic wavefront pressure produces measurable phase differences in the light waves guided by optical fiber.
A fiber-optic hydrophone typically includes a hollow, air-backed element known as a mandrel, with optical fiber wound on the mandrel surface. The advantages of multiple, smaller, interconnected mandrels when compared to a single larger mandrel, are presented in U.S. Pat. No. 5,317,544, and such advantages include increased sensitivity and system robustness during deployment. Although prior art discusses the need to connect multiple mandrel-wound hydrophones in series with a single fiber, the interlink's design and material is often ignored. U.S. Pat. No. 5,317,544 mentions a means for compliantly connecting adjacent hydrophone components, while U.S. Pat. No. 5,475,216 claims a neoprene spacer, and U.S. Pat. No. 5,155,548 describes a spacer preferably formed of neoprene. Neoprene spacers or interlinks induce undesirable phase noise in the sensing fiber.
There is currently not a hydrophone interlink that accomplishes the dual objectives of allowing the hydrophone array to bend as the array passes around small diameter handling sheaves during deployment, while also protecting the fiber between hydrophone elements during post-deployment so as to minimize phase noise along the interlink. What is needed is an interlink that is flexible during deployment, but during post-deployment (i.e., operation), ensures minimal fiber stretching due to array noise sources including acoustic noise, longitudinal stretching, pressure, and bending.